In recent years, silicon carbide (SiC) has been increasingly employed as a material for a semiconductor device in order to allow a higher breakdown voltage, lower loss and the like of the semiconductor device. Silicon carbide is a wide band gap semiconductor having a band gap wider than that of silicon which has been conventionally and widely used as a material for a semiconductor device. By employing the silicon carbide as a material for a semiconductor device, therefore, a higher breakdown voltage, lower on-resistance and the like of the semiconductor device can be achieved. A semiconductor device made of silicon carbide is also advantageous in that performance degradation is small when used in a high-temperature environment as compared to a semiconductor device made of silicon.
Since silicon carbide has an extremely low impurity diffusion coefficient, it is difficult to dope the silicon carbide with an impurity through a thermal diffusion process. Methods of forming an active region in a silicon carbide material include a method of implanting on into an epitaxial growth layer, and an epitaxial growth method involving the addition of impurities using a &want gas (see Japanese Patent Laying-Open No. 2002-280573 (PTD 1), for example).
Generally, when forming an n type epitaxial layer on a silicon carbide substrate, nitrogen (N2) gas is used as a dopant gas. A growth temperature during this process is generally approximately not less than 1400° C. and not more than 1700° C.
Nitrogen molecules include a triple bond between nitrogen atoms, however. It is thus difficult to thermally decompose nitrogen molecules and introduce nitrogen atoms as an active species into the silicon carbide epitaxial layer.